Am486: The Last Clone

The 486 was the last clone of an Intel processor. AMD produced 486s in two different versions—one with microcode by Intel and another with microcode by AMD, because the company was having legal hassles with Intel by that point. In addition to processors sold under the 486 designation, AMD also marketed an AMD 5x86, which was a 486 with a 4x clock multiplier. Running at 133 MHz, this model was compatible with 486 motherboards, but had the performance of a Pentium 75. It was with the 5x86 that AMD began using the famous “Pentium Rating” (5x86 PR 75), which it would stay with up to and including the Athlon 64 X2.